Devices including gate spacer with gap or void and methods of forming the same

ABSTRACT

Devices and structures that include a gate spacer having a gap or void are described along with methods of forming such devices and structures. In accordance with some embodiments, a structure includes a substrate, a gate stack over the substrate, a contact over the substrate, and a spacer disposed laterally between the gate stack and the contact. The spacer includes a first dielectric sidewall portion and a second dielectric sidewall portion. A void is disposed between the first dielectric sidewall portion and the second dielectric sidewall portion.

BACKGROUND

Semiconductor manufacturers face a constant challenge to comply withMoore's Law. Semiconductor manufacturers constantly strive tocontinually decrease feature sizes, such as sizes of active and passivedevices, interconnecting wire widths and thicknesses, and powerconsumption as well as increase device density, wire density, andoperating frequencies.

With decreased feature sized and increased density, conductivecomponents within a device generally have become closer in proximity. Insome instances, this decrease in proximity of conductive components canadversely impact parasitic capacitance within the device. Increases inparasitic capacitance can decrease device operational speed.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is an example of a generic fin Field-Effect Transistor (finFET)in a three-dimensional view in accordance with some embodiments.

FIGS. 2A, 2B, 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B,10A, 10B, 11A, and 11B are cross-sectional views of intermediate stagesin the manufacturing of finFETs in accordance with some embodiments.

FIGS. 11C and 11D are layout views of the structure illustrated in FIGS.11A and 11B in accordance with some embodiments.

FIGS. 12A, 12B, 13A, and 13B are cross-sectional views of intermediatestages in the manufacturing of finFETs in accordance with some otherembodiments.

FIGS. 14A, 14B, 15A, 15B, 16A, 16B, 17A, 17B, 18A, 18B, 19A, 19B, 20A,20B, 21A, and 21B are cross-sectional views of intermediate stages inthe manufacturing of finFETs in accordance with some furtherembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Fin Field-Effect Transistors (finFETs) and methods of forming the sameare provided in accordance with various embodiments. Intermediate stagesof forming finFETs are illustrated. Some embodiments discussed hereinare discussed in the context of finFETs formed using a gate-lastprocess. Some embodiments contemplate aspects used in planar devices,such as planar FETs. Some variations of the embodiments are discussed.One of ordinary skill in the art will readily understand othermodifications that may be made that are contemplated within the scope ofother embodiments. Although method embodiments are discussed in aparticular order, various other method embodiments may be performed inany logical order and may include fewer or more steps described herein.

FIG. 1 illustrates an example of a generic finFET 20 in athree-dimensional view. The finFET 20 comprises a fin 26 on a substrate22. The substrate 22 includes isolation regions 24, and the fin 26protrudes above and from between neighboring isolation regions 24. Agate dielectric 28 is along sidewalls and over a top surface of the fin26, and a gate electrode 30 is over the gate dielectric 28. Source/drainregions 32 and 34 are disposed in opposite sides of the fin 26 withrespect to the gate dielectric 28 and gate electrode 30. FIG. 1 furtherillustrates reference cross-sections that are used in later figures.Cross-section A-A is along a longitudinal axis of the fin 26 and in adirection of, for example, a current flow between the source/drainregions 32 and 34. Cross-section B-B is perpendicular to cross-sectionA-A and is across a channel, gate dielectric 28, and gate electrode 30of the finFET 20. Subsequent figures refer to these referencecross-sections for clarity.

FIGS. 2A-B through 11A-B are cross-sectional views of intermediatestages in the manufacturing of finFETs in accordance with an exemplaryembodiment. Figures ending with an “A” illustrate referencecross-section A-A illustrated in FIG. 1, except for multiple transistorsin one fin. Figures ending with a “B” illustrate reference cross-sectionB-B illustrated in FIG. 1, except for multiple fins.

FIGS. 2A and 2B illustrate a substrate 40. The substrate 40 may be asemiconductor substrate, such as a bulk semiconductor substrate, asemiconductor-on-insulator (SOI) substrate, a multi-layered or gradientsubstrate, or the like. The substrate 40 may include a semiconductormaterial, such as an elemental semiconductor including Si and Ge; acompound or alloy semiconductor including SiC, SiGe, GaAs, GaP, GaAsP,AlInAs, AlGaAs, GaInAs, InAs, GaInP, InP, InSb, and/or GaInAsP; or acombination thereof. The substrate 40 may be doped or un-doped. In aspecific example, the substrate 40 is a bulk silicon substrate.

FIGS. 3A and 3B illustrate the formation of fins 42 and isolationregions 44 between neighboring fins 42. In FIGS. 3A and 3B, fins 42 areformed in the substrate 40. In some embodiments, the fins 42 may beformed in the substrate 40 by etching trenches in the substrate 40. Theetching may be any acceptable etch process, such as a reactive ion etch(RIE), neutral beam etch (NBE), the like, or a combination thereof. Theetch may be anisotropic.

An insulation material is formed in the trenches and between neighboringfins 42 to form the isolation regions 44. The insulation material may bean oxide, such as silicon oxide, a nitride, the like, or a combinationthereof, and may be formed by a high density plasma chemical vapordeposition (HDP-CVD), a flowable CVD (FCVD) (e.g., a CVD-based materialdeposition in a remote plasma system and post curing to make it convertto another material, such as an oxide), the like, or a combinationthereof. Other insulation materials formed by any acceptable process maybe used. In the illustrated embodiment, the insulation material issilicon oxide formed by a FCVD process. An anneal process may beperformed once the insulation material is formed. A planarizationprocess, such as a chemical mechanical polish (CMP), may remove anyexcess insulation material and form top surfaces of the insulationmaterial and top surfaces of the fins 42 that are co-planar.

Although not specifically illustrated, appropriate wells may be formedin the fins 42 and/or substrate 40. For example, a p-well may be formedin a first region of the substrate 40 where n-type devices, such asn-type finFETs, are to be formed, and an n-well may be formed in asecond region of the substrate 40 where p-type devices, such as p-typefinFETs, are to be formed.

For example, to form a p-well in the first region, a photoresist canformed over the fins 42 and the insulation material in the second regionof the substrate 40. The photoresist can be patterned to expose thefirst region of the substrate 40. The photoresist can be formed by usinga spin-on technique and can be patterned using acceptablephotolithography techniques. Once the photoresist is patterned, a p-typeimpurity implant can be performed in the first region, and thephotoresist may act as a mask to substantially prevent p-type impuritiesfrom being implanted into the second region. The p-type impurities maybe boron, BF₂, or the like implanted in the first region to aconcentration of equal to or less than 10¹⁸ cm⁻³, such as between about10¹⁷ cm⁻³ and about 10¹⁸ cm⁻³. After the implant, the photoresist can beremoved, such as by an acceptable ashing process.

Further, to form an n-well in the second region, a photoresist can beformed over the fins 42 and the insulation material in the first regionof the substrate 40. The photoresist can be patterned to expose thesecond region of the substrate 40. The photoresist can be formed byusing a spin-on technique and can be patterned using acceptablephotolithography techniques. Once the photoresist is patterned, ann-type impurity implant may be performed in the second region, and thephotoresist may act as a mask to substantially prevent n-type impuritiesfrom being implanted into the first region. The n-type impurities may bephosphorus, arsenic, or the like implanted in the second region to aconcentration of equal to or less than 10¹⁸ cm⁻³, such as between about10¹⁷ cm⁻³ and about 10¹⁸ cm⁻³. After the implant, the photoresist can beremoved, such as by an acceptable ashing process. After the implants, ananneal may be performed to activate the p-type and n-type impuritiesthat were implanted. The implantations may form a p-well in the firstregion and an n-well in the second region.

The insulation material is recessed to form the isolation regions 44,which may be Shallow Trench Isolation (STI) regions. The insulationmaterial is recessed such that fins 42 protrude from between neighboringisolation regions 44. The recessing may use an acceptable etchingprocess, such as one that is selective to the material of the isolationregions 44. For example, a chemical oxide removal using a CERTAS® etchor an Applied Materials SICONI tool or dilute hydrofluoric (dHF) acidmay be used.

A person having ordinary skill in the art will readily understand thatthe process described with respect to FIGS. 2A, 2B, 3A, and 3B is justone example of how fins may be formed. In other embodiments, adielectric layer can be formed over a top surface of the substrate 40;trenches can be etched through the dielectric layer; epitaxial fins canbe epitaxially grown in the trenches; and the dielectric layer can berecessed such that the homoepitaxial and/or heteroepitaxial structuresprotrude from the dielectric layer to form epitaxial fins. It may beadvantageous to epitaxially grow a material or epitaxial fin structurefor n-type finFETs different from the material or epitaxial finstructure for p-type finFETs.

In FIGS. 4A and 4B, a dummy dielectric layer is formed on the fins 42.The dummy dielectric layer may be, for example, silicon oxide, siliconnitride, a combination thereof, or the like, and may be deposited orthermally grown according to acceptable techniques, such as CVD, thermaloxidation, or the like. A dummy gate layer is formed over the dummydielectric layer. The dummy gate layer may be deposited, such as byusing CVD or the like, over the dummy dielectric layer and thenplanarized, such as by a CMP. The dummy gate layer may comprise, forexample, polysilicon, although other materials that have a high etchingselectivity may also be used. A mask layer is formed over the dummy gatelayer. The mask layer may be deposited, such as by using CVD or thelike, over the dummy gate layer. The mask layer may comprise, forexample, silicon nitride, silicon oxynitride, silicon carbon nitride, orthe like.

The mask layer may be patterned using acceptable photolithography andetching techniques to form masks 50. The pattern of the masks 50 thenmay be transferred to the dummy gate layer and dummy dielectric layer byan acceptable etching technique to form dummy gates 48 and dummy gatedielectrics 46 from the dummy gate layer and the dummy dielectric layer,respectively. The etching may comprise an acceptable anisotropicetching, such as RIE, NBE, or the like. The dummy gates 48 coverrespective channel regions of the fins 42. The dummy gates 48 may alsohave a lengthwise direction substantially perpendicular to thelengthwise direction of respective fins 42.

Implants for lightly doped source/drain (LDD) regions 52 may beperformed. Similar to the implants discussed above, a mask, such as aphotoresist, may be formed over the second region, e.g., for p-typedevices, while exposing the first region, e.g., for n-type devices, andn-type impurities may be implanted into the exposed fins 42 in the firstregion. The mask may then be removed. Subsequently, a mask, such as aphotoresist, may be formed over the first region while exposing thesecond region, and p-type impurities may be implanted into the exposedfins 42 in the second region. The mask may then be removed. The n-typeimpurities may be any of the n-type impurities previously discussed, andthe p-type impurities may be any of the p-type impurities previouslydiscussed. The LDD regions 52 may have a concentration of impuritiesfrom about 10¹⁵ cm⁻³ to about 10¹⁶ cm⁻³. An anneal may be used toactivate the implanted impurities.

Further in FIGS. 4A and 4B, dummy gate spacers 54 are formed alongsidewalls of the dummy gates 48, dummy gate dielectrics 46, and masks50. The dummy gate spacers 54 may be formed by conformally depositing,such as by CVD or the like, a layer and subsequently anisotropicallyetching the layer. The material of the dummy gate spacers 54 may be anyappropriate material, such as aluminum oxide (Al₂O₃) or the like, thatcan be selectively etched relative to other components, as will bediscussed subsequently.

Epitaxial source/drain regions 56 are formed in the source/drain regionsof the fins 42. The epitaxial source/drain regions 56 are formed in thesource/drain regions of the fins 42 such that each dummy gate 48 isdisposed between ones of a respective pair of the epitaxial source/drainregions 56 in the fin 42.

The epitaxial source/drain regions 56 in the first region, e.g., forn-type devices, may be formed by masking, such as with a hard mask, thesecond region, e.g., for p-type devices. Then, source/drain regions ofthe fins 42 in the first region are etched to form recesses. The etchmay be any appropriate etch selective to the fins 42 and may beanisotropic. The epitaxial source/drain regions 56 in the first regionare then epitaxially grown in the recesses. The epitaxial growth may beby using Metal-Organic CVD (MOCVD), Molecular Beam Epitaxy (MBE), LiquidPhase Epitaxy (LPE), Vapor Phase Epitaxy (VPE), the like, or acombination thereof. The epitaxial source/drain regions 56 in the firstregion may comprise any acceptable material, such as appropriate forn-type finFETs. For example, the epitaxial source/drain regions 56 inthe first region may comprise silicon, SiC, SiCP, SiP, or the like. Theepitaxial source/drain regions 56 may have surfaces raised fromrespective outer surfaces of the fins 42 and may have facets. The maskmay then be removed, such as by using an etch selective to the materialof the mask.

The epitaxial source/drain regions 56 in the second region may be formedby masking, such as with a hard mask, the first region. Then,source/drain regions of the fins 42 in the second region are etched toform recesses. The etch may be any appropriate etch selective to thefins 42 and may be anisotropic. The epitaxial source/drain regions 56 inthe second region are then epitaxially grown in the recesses. Theepitaxial growth may be by using MOCVD, MBE, LPE, VPE, the like, or acombination thereof. The epitaxial source/drain regions 56 in the secondregion may comprise any acceptable material, such as appropriate forp-type finFETs. For example, the epitaxial source/drain regions 56 inthe second region may comprise SiGe, SiGeB, Ge, GeSn, or the like. Theepitaxial source/drain regions 56 may have surfaces raised fromrespective outer surfaces of the fins 42 and may have facets. The maskmay then be removed, such as by using an etch selective to the materialof the mask.

The epitaxial source/drain regions 56 and/or source/drain regions of thefins 42 may be implanted with dopants, similar to the process previouslydiscussed for forming LDD regions 52, followed by an anneal. Thesource/drain regions may have an impurity concentration of between about10¹⁹ cm⁻³ and about 10²¹ cm⁻³. The n-type impurities for source/drainregions in the first region, e.g., for n-type devices, may be any of then-type impurities previously discussed, and the p-type impurities forsource/drain regions in the second region, e.g., for p-type devices, maybe any of the p-type impurities previously discussed. In otherembodiments, the epitaxial source/drain regions 56 may be in situ dopedduring growth.

FIG. 4A illustrates cross-section B-B that is the cross-sectionillustrated by FIG. 4B, and FIG. 4B illustrates cross-section A-A thatis the cross-section illustrated by FIG. 4A. These relationships betweenthe depicted cross-sections in FIGS. 4A and 4B continue through thefollowing figures although not specifically illustrated subsequently.

In FIGS. 5A and 5B, an etch stop layer (ESL) 58 is conformally formed onepitaxial source/drain regions 56, dummy gate spacers 54, masks 50, andisolation regions 44. In some embodiments, the ESL 58 may comprisesilicon nitride, silicon carbonitride, or the like, formed using AtomicLayer Deposition (ALD), chemical vapor deposition (CVD), the like, or acombination thereof. A bottom inter-layer dielectric (ILD0) 60 isdeposited over the ESL 58. ILD0 60 may comprise Phospho-Silicate Glass(PSG), Boro-Silicate Glass (BSG), Boron-Doped Phospho-Silicate Glass(BPSG), undoped Silicate Glass (USG), or the like, and may be depositedby any suitable method, such as CVD, plasma-enhanced CVD (PECVD), FCVD,the like, or a combination thereof.

In FIGS. 6A and 6B, a planarization process, such as a CMP, is performedto level the top surface of ILD0 60 with the top surfaces of the dummygates 48. The CMP may also remove the masks 50 and the ESL 58 from overthe dummy gates 48. Accordingly, top surfaces of the dummy gates 48 areexposed through the ILD0 60. The dummy gates 48 and the dummy gatedielectrics 46 are removed in an etching step(s), so that openingsthrough the ILD0 60 and defined by the dummy gate spacers 54 are formedto the fins 42. Each opening exposes a channel region of a respectivefin 42. Each channel region is disposed between ones of neighboringpairs of epitaxial source/drain regions 56. The etching step(s) may beselective to the materials of the dummy gates 48 and the dummy gatedielectrics 46, which etching may be a dry or wet etching. During theetching, the dummy gate dielectrics 46 may be used as an etch stop layerwhen the dummy gates 48 are etched. The dummy gate dielectric 46 maythen be etched after the removal of the dummy gates 48.

An interfacial dielectric 62 is formed in each opening and on the fins42. The interfacial dielectric 62 may be, for example, an oxide or thelike formed by thermal oxidation or the like. A gate dielectric layer 64is then formed conformally on the top surface of the ILD0 60 and in theopenings along sidewalls of the dummy gate spacers 54 and on theinterfacial dielectric 62. In some embodiments, the gate dielectriclayer 64 comprises a high-k dielectric material, and in theseembodiments, the gate dielectric layer 64 may have a k value greaterthan about 7.0, and may include a metal oxide or a silicate of Hf, Al,Zr, La, Mg, Ba, Ti, Pb, and combinations thereof. The formation methodsof gate dielectric layer 64 may include ALD, CVD, Molecular-BeamDeposition (MBD), the like, or a combination thereof.

A gate electrode 66 is formed on the gate dielectric layer 64 and in theopenings. The gate electrode 66 may comprise a single material or anycombination of layers and different materials as may be appropriate. Forexample, the gate electrode material may comprise a capping layer, oneor more work function tuning layers, one or more barrier layer, and oneor more metal.

A capping layer can be formed conformally on the gate dielectric layer64. The capping layer can comprise a first sub-layer and a secondsub-layer. In some embodiments, the capping layer may be a single layeror may comprise additional sub-layers. The capping layer may function asa barrier layer to prevent a subsequently deposited metal-containingmaterial from diffusing into the gate dielectric layer 64. Further, thesecond sub-layer can function as an etch stop during the formation ofwork function tuning layers in various regions if the first sub-layer isformed from a same material as the work function tuning layers and ifdifferent work function tuning layers are to be formed in the variousregions. The first sub-layer can comprise titanium nitride (TiN) or thelike deposited conformally on the gate dielectric layer 64 by ALD, CVD,or the like. The second sub-layer can comprise tantalum nitride (TaN) orthe like deposited conformally on the first sub-layer by ALD, CVD, orthe like.

One or more work function tuning layer can be formed conformally on thecapping layer, e.g., on the second sub-layer. The first work functiontuning layer may be any acceptable material to tune a work function of adevice to a desired amount given the application of the device to beformed, and may be deposited using any acceptable deposition process. Insome embodiments, the work function tuning layer comprises titaniumaluminum (TiAl), titanium nitride (TiN), or the like deposited by ALD,CVD, or the like.

A metal can be deposited in the openings on the work function tuninglayer(s). The metal can be an elemental metal, an alloy of metals,multiple layers of elemental metal, or a combination thereof, and caninclude tungsten (W), aluminum (Al), cobalt (Co), ruthenium (Ru), acombination thereof or the like. The metal can be deposited using CVD,physical vapor deposition (PVD), the like, or a combination thereof. Themetal at least fills the remaining portions of the openings.

In FIGS. 7A and 7B, a planarization process, such as a CMP, may beperformed to remove the excess portions of the gate electrode 66 andgate dielectric layer 64, which excess portions are over the top surfaceof ILD0 60. Then, a controlled etch-back selective to the gate electrode66 and gate dielectric layer 64 is performed to recess the gateelectrode 66 and gate dielectric layer 64 from the top surface of theILD0 60. First dielectric caps 68 are then formed on the gate electrode66 and gate dielectric layer 64. To form the first dielectric caps 68, afirst cap dielectric layer can be deposited in the remaining portions ofthe openings above the gate electrode 66 and gate dielectric layer 64(e.g., after recessing the gate electrode 66 and gate dielectric layer64) and on the top surface of the ILD0 60. The first cap dielectriclayer may comprise silicon carbide, silicon nitride, siliconcarbonitride, or the like, formed using CVD, PECVD, or the like. Thefirst cap dielectric layer can include any appropriate material thatallows for etch selectivity between the first dielectric caps 68 and thedummy gate spacers 54. In a specific example, the first dielectric caps68 are silicon carbide (SiC), and the dummy gate spacers 54 are aluminumoxide (Al₂O₃). The first cap dielectric layer can then be planarized,such as by CMP, to form top surfaces co-planar with the top surface ofthe ILD0 60 thereby forming the first dielectric caps 68. A thickness ofthe first dielectric caps 68 can be in a range from about 3 nm to about20 nm, such as about 5 nm.

In FIGS. 8A and 8B, lower contacts 70 are formed through the ILD0 60 andthe ESL 58 to the epitaxial source/drain regions 56. Openings for thelower contacts 70 are formed through the ILD0 60 and the ESL 58. Theopenings may be formed using acceptable photolithography and etchingtechniques. The ESL 58 along the dummy gate spacers 54 at the openingmay be removed by the etching, such as if the ESL 58 is sufficientlythin, as illustrated in FIG. 8A. A liner, such as a diffusion barrierlayer or the like, and a conductive material are formed in the openings.The liner may include titanium, titanium nitride, tantalum, tantalumnitride, or the like. The conductive material may be tungsten, copper, acopper alloy, silver, gold, tungsten, aluminum, nickel, or the like. Aplanarization process, such as a CMP, may be performed to remove excessmaterial from the top surfaces of the ILD0 60, dummy gate spacers 54 andthe first dielectric caps 68. The remaining liner and conductivematerial form lower contacts 70 in the openings. An anneal process maybe performed to form a silicide at the interface between the epitaxialsource/drain regions 56 and the lower contacts 70.

In FIGS. 9A and 9B, a controlled etch-back selective to the lowercontacts 70 is performed to recess the lower contacts 70 from the topsurface of the dummy gate spacers 54 and the first dielectric caps 68.As illustrated, the recessing can also recess the ILD0 60. Seconddielectric caps 72 are then formed on the lower contacts 70. To form thesecond dielectric caps 72, a second cap dielectric layer can bedeposited in the recesses formed by recessing the lower contacts 70 andon the ILD0 60. The second cap dielectric layer may comprise siliconnitride, silicon carbonitride, silicon carbide, or the like, formedusing CVD, PECVD, or the like. The second cap dielectric layer caninclude any appropriate material that allows for etch selectivitybetween the first dielectric caps 68, the second dielectric caps 72, andthe dummy gate spacers 54. Continuing the specific example where thefirst dielectric caps 68 and the dummy gate spacers 54 are siliconcarbide (SiC) and aluminum oxide (Al₂O₃), respectively, the seconddielectric caps 72 are silicon nitride (SiN). The second cap dielectriclayer can then be planarized, such as by CMP, to form top surfacesco-planar with the top surfaces of the dummy gate spacers 54 and thefirst dielectric caps 68 thereby forming the second dielectric caps 72.A thickness of the second dielectric caps 72 can be in a range fromabout 3 nm to about 20 nm, such as about 5 nm.

After processing through FIGS. 9A and 9B, the dummy gate spacers 54 canhave a width W, a first height H1, and a second height H2. The width Wcan correspond to the thickness of the layer that was deposited andsubsequently etched to form the dummy gate spacers 54. The width W canbe in a range from about 1 nm to about 5 nm, such as about 3 nm. Thefirst height H1 is from a top surface of the fins 42 to a top surface ofthe dummy gate spacers 54. The first height H1 can be in a range fromabout 30 nm to about 80 nm, such as about 50 nm. The second height H2 isfrom a top surface of the isolation regions 44 to the top surface of thedummy gate spacers 54. The second height H2 can be in a range from about80 nm to about 130 nm, such as about 100 nm. A first aspect ratio of thewidth W to the first height H1 can be in a range from about 6 to about80, such as about 17. A second aspect ratio of the width W to the secondheight H2 can be in a range from about 16 to about 130, such as about33.

In FIGS. 10A and 10B, the dummy gate spacers 54 are removed, and gatespacers 74 with respective gaps or voids 76 are formed where the dummygate spacers 54 were removed. The dummy gate spacers 54 may be removedusing an appropriate etch selective to the material of the dummy gatespacers 54, which etch may not significantly etch the first dielectriccaps 68 and the second dielectric caps 72. The etch may be, for example,a wet etch, and may be isotropic. The entirety of the dummy gate spacers54 may be removed, which is what is depicted in FIGS. 10A and 10B. Inother words, the dummy gate spacers 54 are removed from along the entiresecond height H2. The removal of the dummy gate spacers 54 results in anopening encircling each gate stack (e.g., a combination of a respectivegate dielectric layer 64 and gate electrode 66), and between each gatestack and a respective adjacent lower contact 70 and/or remainingportions of the ILD0 60. In this embodiment, the openings have aspectratios corresponding to the aspect ratios of the dummy gate spacers 54that were previously discussed.

The gate spacers 74 are then formed in the openings. The gate spacers 74can be an appropriate dielectric material, which may further be a low-kdielectric layer that has a dielectric constant (k) value less than 3.9,which may further be less than 2.0. In some embodiments, the dielectricmaterial of the gate spacers 74 is silicon carbon oxynitride (SiCON),silicon oxycarbide (SiOC), or the like. The dielectric material of thegate spacers 74 can be selectively etched relative to the firstdielectric caps 68 and the second dielectric caps 72. The gate spacers74 can be formed using an appropriate deposition technique, such as ALD,CVD, or the like. The deposition may be substantially conformal suchthat a layer of the dielectric material of the gate spacers 74 isdeposited with a substantially same thickness along the sidewalls andbottom surfaces of the openings. Due to the high aspect ratios of theopenings, the deposition may result in a larger deposition rate at anupper portion of the opening than at a lower portion of the opening.Hence, the layer of the dielectric material may pile-up or neck at theupper portion of the opening before a lower portion of the opening isfilled with the dielectric material causing the opening to bepinched-off before being completely filled. Respective gaps or voids 76can therefore be formed within the dielectric material of the gatespacers 74. A gas, such as a gas(es) used during the deposition of thedielectric material of the gate spacers 74 or any other species that candiffuse into the gaps or voids 76, may be in the gaps or voids 76. In aregion of the gate spacer 74 between the gate stack and the lowercontacts 70, a height H3 of the gaps or voids 76 (e.g., from a bottomsurface to a top surface containing the gap or void 76) can be in arange from about 0.3 times the first height H1 to about 0.7 times thefirst height H1. A planarization process, such as a CMP, may beperformed to remove excess dielectric material of the gate spacers 74from the top surfaces of the first dielectric caps 68 and the seconddielectric caps 72.

In FIGS. 11A and 11B, an upper ILD (ILD1) 80 is deposited over the firstdielectric caps 68, second dielectric caps 72, and gate spacers 74. ILD180 is formed of a dielectric material such as PSG, BSG, BPSG, USG, orthe like, and may be deposited by any suitable method, such as CVD andPECVD.

First upper contacts 82 and second upper contacts 84 are then formed tothe lower contacts 70 and the gate electrode 66, respectively. Openingsfor first upper contacts 82 are formed through the ILD1 80 and thesecond dielectric caps 72 to the lower contacts 70. The openings may beformed using acceptable photolithography and etching techniques. Aliner, such as a diffusion barrier layer, an adhesion layer, or thelike, and a conductive material are formed in the openings. The linermay include titanium, titanium nitride, tantalum, tantalum nitride, orthe like. The conductive material may be copper, a copper alloy, silver,gold, tungsten, aluminum, nickel, or the like. A planarization process,such as a CMP, may be performed to remove excess material from a surfaceof the ILD1 80. The remaining liner and conductive material form firstupper contacts 82 in the openings and to the lower contacts 70. Then,openings for second upper contacts 84 are formed through the ILD1 80 andthe first dielectric caps 68 to the gate electrode 66. The openings maybe formed using acceptable photolithography and etching techniques. Aliner, such as a diffusion barrier layer, an adhesion layer, or thelike, and a conductive material are formed in the openings. The linermay include titanium, titanium nitride, tantalum, tantalum nitride, orthe like. The conductive material may be copper, a copper alloy, silver,gold, tungsten, aluminum, nickel, or the like. A planarization process,such as a CMP, may be performed to remove excess material from a surfaceof the ILD1 80. The remaining liner and conductive material form secondupper contacts 84 in the openings and to the gate electrode 66.

FIGS. 11A and 11B illustrate cross-sections C-C and D-D. Cross-sectionC-C is depicted by the layout view of FIG. 11C, and cross-section D-D isdepicted by the layout view of FIG. 11D. FIGS. 11C and 11D illustratecross-sections A-A and B-B that are depicted by FIGS. 11A and 11B,respectively. Cross-section C-C is at a lower vertical level thancross-section D-D. Cross-section C-C intersects the gate electrode 66,the gate dielectric layers 64, the gate spacers 74, the gaps or voids76, and the lower contacts 70. Cross-section D-D intersects the firstdielectric caps 68, the second dielectric caps 72, the gate spacers 74,the first upper contacts 82, and the second upper contacts 84.

FIGS. 11C and 11D illustrate that the gate spacers 74 encircle arespective gate stack (e.g., gate dielectric layer 64 and gate electrode66). Further, FIG. 11C illustrates that the gaps or voids 76 within thegate spacers 74 can also encircle a respective gate stack.

Although not explicitly shown, a person having ordinary skill in the artwill readily understand that further processing steps may be performedon the structure in FIGS. 11A and 11B. For example, various Inter-MetalDielectrics (IMD) and their corresponding metallizations may be formedover ILD1 80.

FIGS. 12A-B and 13A-B are cross-sectional views of intermediate stagesin the manufacturing of finFETs in accordance with another exemplaryembodiment. The manufacturing process in FIGS. 12A-B and 13A-B shows amodification to the manufacturing process of FIGS. 2A-B and 11A-B.Processing proceeds as discussed above with respect to FIGS. 2A-Bthrough FIGS. 9A-B. In FIGS. 11A and 11B, at least portions of the dummygate spacers 54 are removed, and gate spacers 74 with respective gaps orvoids 76 are formed where the portions of the dummy gate spacers 54 wereremoved. As with FIGS. 10A and 10B, the dummy gate spacers 54 may beremoved using an appropriate etch selective to the material of the dummygate spacers 54. In FIG. 12B, the entirety of the dummy gate spacers 54is not removed. As shown, the dummy gate spacers 54 are only removedfrom along the entire first height H1, e.g., above the plane of the topsurfaces of the fins 42. The dummy gate spacers 54 at and below theplane of the top surfaces of the fins 42 remains. As with FIG. 10A and10B, the removal of the dummy gate spacers 54 results in an openingencircling each gate stack, and between each gate stack and a respectiveadjacent lower contact 70 and/or remaining portions of the ILD0 60. Inthis embodiment, the openings have aspect ratios corresponding to theaspect ratio of the width W to the first height H1 of the dummy gatespacers 54 that was previously discussed. Some embodiments contemplatethat any amount of the dummy gate spacers 54 can be removed and canremain after the removal.

As in FIGS. 10A and 10B, the gate spacers 74 are then formed in theopenings. Due to the high aspect ratios of the openings, the depositionof the dielectric material of the gate spacers 74 may result in a largerdeposition rate at an upper portion of the opening than at a lowerportion of the opening. Hence, as discussed above, respective gaps orvoids 76 can therefore be formed within the dielectric material of thegate spacers 74. A gas, such as a gas(es) used during the deposition ofthe dielectric material of the gate spacers 74 or any other species thatcan diffuse into the gaps or voids 76, may be in the gaps or voids 76. Aplanarization process, such as a CMP, may be performed to remove excessdielectric material of the gate spacers 74 from the top surfaces of thefirst dielectric caps 68 and the second dielectric caps 72.

In FIGS. 13A and 13B, ILD0 80, first upper contacts 82, and second uppercontacts 84 are formed as discussed with respect to FIGS. 11A and 11B.It is worth noting that the layout views of FIGS. 11C and 11D are thesame with this depicted modification in FIGS. 12A-B and 13A-B.

FIGS. 14A-B through 21A-B are cross-sectional views of intermediatestages in the manufacturing of finFETs in accordance with anotherexemplary embodiment. Processing proceeds as discussed above withrespect to FIGS. 2A-B through FIGS. 3A-B. Processing continues asdiscussed above with respect to FIGS. 4A-B, except that, instead offorming dummy gate spacers 54, multi-layer gate spacers 90 are formed.In FIGS. 14A and 14B, multi-layer gate spacers 90 are formed alongsidewalls of the dummy gates 48, dummy gate dielectrics 46, and masks50. The multi-layer gate spacers 90 comprise a first sub-layer 92 on thesidewalls of the dummy gates, 48, dummy gate dielectrics 46, and masks50; a dummy second sub-layer 94 on the first sub-layer 92; and a thirdsub-layer 96 on the dummy second sub-layer 94. Each of the sub-layers92, 94, and 96 may be formed by conformally depositing, such as by CVDor the like, and anisotropically etching the respective sub-layer. Thematerials of the first sub-layer 92 and the third sub-layer 96 may beany appropriate dielectric materials, which may be the same ordifferent, such as silicon nitride, silicon carbon nitride, siliconoxynitride, or the like. The material of the dummy second sub-layer 94may be any appropriate material, such as aluminum oxide (Al₂O₃) or thelike, that can be selectively etched relative to the first sub-layer 92,the third sub-layer 96, and other components, as will be discussedsubsequently.

Processing continues in FIGS. 15A-B through 19A-B as discussed abovewith respect to FIGS. 5A-B through 9A-B, respectively, except with themulti-layer gate spacers 90 replacing the dummy spacer 54. Afterprocessing through FIGS. 19A and 19B, the multi-layer gate spacers 90can have a width W, a first height H1, and a second height H2. The widthW can correspond to the combined thicknesses of the first sub-layer 92,the dummy second sub-layer 94, and the third sub-layer 96 that weredeposited and subsequently etched to form the multi-layer gate spacers90. The width W can be in a range from about 4 nm to about 10 nm, suchas about 6 nm. The thickness of the first sub-layer 92 can be in a rangefrom about 1 nm to about 3 nm, such as about 2 nm. The thickness of thedummy second sub-layer 94, which is illustrated as width Wb, can be in arange from about 2 nm to about 4 nm, such as about 2 nm. The thicknessof the third sub-layer 96 can be in a range from about 1 nm to about 3nm, such as about 2 nm. The first height H1 is from a top surface of thefins 42 to a top surface of the multi-layer gate spacers 90. The firstheight H1 can be in a range from about 30 nm to about 80 nm, such asabout 50 nm. The second height H2 is from a top surface of the isolationregions 44 to the top surface of the multi-layer gate spacers 90. Thesecond height H2 can be in a range from about 80 nm to about 130 nm,such as about 100 nm. A first aspect ratio of the width W of themulti-layer gate spacers 90 to the first height H1 can be in a rangefrom about 3 to about 20, such as about 8. A second aspect ratio of thewidth W of the multi-layer gate spacers 90 to the second height H2 canbe in a range from about 8 to about 33, such as about 17. A third aspectratio of the width Wb of the dummy second sub-layer 94 to the firstheight H1 can be in a range from about 7 to about 20, such as about 25.A fourth aspect ratio of the width Wb of the dummy second sub-layer 94to the second height H2 can be in a range from about 20 to about 65,such as about 50.

In FIGS. 20A and 20B, the dummy second sub-layers 94 in the multi-layergate spacers 90 are removed, and second sub-layers 98 and gaps or voids100 are formed where the dummy second sub-layers 94 were removed. Thedummy second sub-layers 94 may be removed using an appropriate etchselective to the material of the dummy second sub-layers 94, which etchmay not significantly etch the first dielectric caps 68, the seconddielectric caps 72, the first sub-layers 92, and the third sub-layers96. The etch may be, for example, a wet etch, and may be isotropic. Byhaving the first sub-layers 92 and the third sub-layers 96 remain afterthe dummy second sub-layers 94 are etched, protection may be provided tothe gate stack and the lower contacts 70 during the removal of the dummysecond sub-layers 94. The entirety of the dummy second sub-layers 94 maybe removed, which is what is depicted in FIGS. 20A and 20B. In otherwords, the dummy second sub-layers 94 are removed from along the entiresecond height H2. In other embodiments, the entirety of the dummy secondsub-layers 94 is not removed. The dummy second sub-layers 94 may beremoved from only along the entire first height H1, e.g., above theplane of the top surfaces of the fins 42 such that the dummy secondsub-layers 94 at and below the plane of the top surfaces of the fins 42remains. Some embodiments contemplate that any amount of the dummysecond sub-layers 94 can be removed and can remain after the removal. Aswith FIGS. 10A and 10B, the removal of the dummy second sub-layers 94results in an opening encircling each gate stack, and between the firstsub-layer 92 and the third sub-layer 96 in each of the multi-layer gatespacers 90. In this embodiment, the openings have aspect ratioscorresponding to the aspect ratio of the width Wb of the dummy secondsub-layers 94 to the second height H2 of the multi-layer gate spacers 90that was previously discussed. Other embodiments contemplate otheraspect ratios depending on the amount of the dummy second sub-layers 94that is removed, such as an aspect ratio of the width Wb of the dummysecond sub-layers 94 to the first height H1 of the multi-layer gatespacers 90.

The second sub-layers 98 are then formed in the openings. The secondsub-layers 98 can be an appropriate dielectric material, which mayfurther be a low-k dielectric layer that has a dielectric constant (k)value less than 3.9, which may further be less than 2.0. In someembodiments, the dielectric material of the second sub-layers 98 issilicon carbon oxynitride (SiCON), silicon oxycarbide (SiOC), or thelike. The dielectric material of the second sub-layers 98 can beselectively etched relative to the first dielectric caps 68 and thesecond dielectric caps 72. The second sub-layers 98 can be formed usingan appropriate deposition technique, such as ALD, CVD, or the like. Ifthe aspect ratio of the openings is sufficiently low, the deposition maybe substantially conformal and form gaps or voids as discussed withrespect to FIGS. 10A and 10B. In the illustrated embodiment, due to thehigher aspect ratios of the openings, the deposition may result indeposition occurring substantially only at an upper portion of theopening. Hence, the dielectric material of the second sub-layers 98 maybe deposited at the upper portion of the opening without a significantamount being deposited in a lower portion of the opening. Respectivegaps or voids 100 can therefore be formed below the dielectric materialof the second sub-layers 98 and between the first sub-layer 92 and thethird sub-layer 96. A gas, such as a gas(es) used during the depositionof the dielectric material of the second sub-layers 98 or any otherspecies that can diffuse into the gaps or voids 100, may be in the gapsor voids 100. In a region of the multi-layer gate spacer 90 between thegate stack and the lower contacts 70, a height H4 of the gaps or voids100 can be in a range from about 0.3 times the first height H1 to about0.7 times the first height H1. A planarization process, such as a CMP,may be performed to remove excess dielectric material of the secondsub-layers 98 from the top surfaces of the first dielectric caps 68, thesecond dielectric caps 72, the first sub-layers 92, and the thirdsub-layers 96. As a result, the multi-layer gate spacers 90 include thefirst sub-layers, the second sub-layer 98, and the third sub-layers 96with gaps or voids 100 therein. Processing then continues in FIGS. 21A-Bas discussed above with respect to FIGS. 11A-B.

Some embodiments may achieve advantages. For example, by having a gatespacer formed, at least in part, of a low-k dielectric material,parasitic capacitance between the gate electrode and contacts can bereduced. Further, by having a gap or void formed in the gate spacer, thedielectric constant (k) can be further reduced, thereby reducingparasitic capacitance even further. According to some of the embodimentsdisclosed above, parasitic capacitance between the gate electrode 66 andthe lower contacts 70 can be reduced. These advantages may beadvantageous for reduced technology nodes, such as 10 nm and below.

An embodiment is a structure. The structure includes a substrate, a gatestack over the substrate, a contact over the substrate, and a spacerdisposed laterally between the gate stack and the contact. The spacerincludes a first dielectric sidewall portion and a second dielectricsidewall portion. A void is disposed between the first dielectricsidewall portion and the second dielectric sidewall portion.

Another embodiment is a structure. The structure comprises a substrate,a gate dielectric over the substrate, a gate electrode over the gatedielectric, a gate spacer around the gate electrode, a source/drainregion in the substrate and proximate to the gate dielectric and gateelectrode, and a lower contact connecting to the source/drain region.The gate spacer is disposed between the lower contact and the gateelectrode. The gate spacer comprises a first solid dielectric sidewallportion and a second solid dielectric sidewall portion. A void isbetween the first solid dielectric sidewall portion and the second soliddielectric sidewall portion. The void is around the gate electrode.

A further embodiment is a method. The method comprising forming a firstinter-layer dielectric layer over a substrate; forming a gate stack inthe first inter-layer dielectric layer and over the substrate; forming acontact through the first inter-layer dielectric layer to the substrate;and forming a gate spacer between the gate stack and the contact. Thegate spacer is around the gate stack and has a void around the gatestack.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A structure comprising: a substrate with a fin; agate stack over the fin; a contact over the substrate; and a spacerdisposed laterally between the gate stack and the contact, the spacercomprising a first dielectric sidewall portion and a second dielectricsidewall portion, a void being disposed between the first dielectricsidewall portion and the second dielectric sidewall portion.
 2. Thestructure of claim 1, wherein the first dielectric sidewall portion andthe second dielectric sidewall portion each comprises a low-k dielectricmaterial.
 3. The structure of claim 1, wherein the spacer comprises asolid dielectric material fully enclosing the void within the soliddielectric material, the first dielectric sidewall portion and thesecond dielectric sidewall portion each being a portion of the soliddielectric material.
 4. The structure of claim 1, wherein the spacercomprises a first solid dielectric layer and a second solid dielectriclayer, each of the first solid dielectric layer and the second soliddielectric layer extending vertically from the substrate, the firstsolid dielectric layer being the first dielectric sidewall portion, thesecond solid dielectric layer being the second dielectric sidewallportion, a solid dielectric material being disposed between the firstsolid dielectric layer and the second solid dielectric layer above thevoid.
 5. The structure of claim 1, wherein the void contacts a surfaceof the substrate.
 6. The structure of claim 1, wherein the spacerlaterally encircles the gate stack, and the void laterally encircles thegate stack.
 7. The structure of claim 1, wherein the spacer has a firstheight from a surface of the substrate and in a direction normal to thesurface of the substrate, the void having a second height from a bottomsurface of the void to a top surface of the void, a ratio of the secondheight to the first height being in a range from 0.3 to 0.7.
 8. Thestructure of claim 1 further comprising: a source/drain region in thesubstrate and proximate to the gate stack, the contact connecting to thesource/drain region; a first inter-layer dielectric layer over thesubstrate and laterally around the gate stack, the contact beingdisposed through the first inter-layer dielectric layer; and a secondinter-layer dielectric layer over the first inter-layer dielectriclayer, the contact, the gate stack, and the spacer.
 9. The structure ofclaim 8 further comprising: a first dielectric cap over the contact andthe first inter-layer dielectric layer; and a second dielectric cap overthe gate stack, respective top surfaces of the first dielectric cap, thesecond dielectric cap, and the spacer being co-planar.
 10. A structurecomprising: a substrate; a gate dielectric over the substrate; a gateelectrode over the gate dielectric; a gate spacer around the gateelectrode, the gate spacer comprising a first solid dielectric sidewallportion and a second solid dielectric sidewall portion, a void beingbetween the first solid dielectric sidewall portion and the second soliddielectric sidewall portion, the void being around the gate electrode; asource/drain region in the substrate and proximate to the gatedielectric and gate electrode; and a lower contact connecting to thesource/drain region, the gate spacer being disposed immediately adjacentto the lower contact and between the lower contact and the gateelectrode.
 11. The structure of claim 10, wherein the spacer comprises acontinuous layer enclosing the void, each of the first solid dielectricsidewall portion and the second solid dielectric sidewall portion beinga portion of the continuous layer.
 12. The structure of claim 10,wherein the first solid dielectric sidewall portion is a first layer,and the second solid dielectric sidewall portion is a second layerseparated from the first layer, the void being disposed between thefirst layer and the second layer, the void contacting a surface of thesubstrate, a solid dielectric material being disposed between the firstlayer and the second layer and above the void.
 13. The structure ofclaim 10 further comprising: a first inter-layer dielectric layer overthe substrate, the gate electrode being in the first inter-layerdielectric layer, the lower contact being through the first inter-layerdielectric layer; a first dielectric cap over the gate electrode; asecond dielectric cap over the lower contact, top surfaces of the firstdielectric cap, the second dielectric cap, and the gate spacer beingco-planar; a second inter-layer dielectric layer over the firstdielectric cap, the second dielectric cap, and the gate spacer; a firstupper contact extending through the second inter-layer dielectric layerand the first dielectric cap and connecting to the gate electrode; and asecond upper contact extending through the second inter-layer dielectriclayer and the second dielectric cap and connecting to the lower contact.14. A structure comprising: a gate dielectric over a substrate; a gateelectrode over the gate dielectric; a contact in physical connectionwith the substrate at a point laterally removed from the gate electrode;a dielectric material surrounding the gate electrode and at leastpartially located between the gate electrode and the contact, thedielectric material comprising a first material throughout thedielectric material, wherein the dielectric material comprises a firstsidewall facing the contact, the first sidewall being straight as thefirst sidewall extends from a first side of the dielectric materialfacing the substrate to a second side of the dielectric materialopposite the first side; and a void surrounded by the dielectricmaterial, wherein the void encircles the gate electrode.
 15. Thestructure of claim 14, wherein the dielectric material has a firstheight and the void has a second height that is between about 0.3 and0.7 times the first height.
 16. The structure of claim 14, wherein thevoid exposes a portion of the substrate.
 17. The structure of claim 14,further comprising an inter-layer dielectric surrounding the contact.18. The structure of claim 14, further comprising a dielectric caplocated over the gate electrode.
 19. The structure of claim 18, whereinthe dielectric cap has a top surface that is planar with a top surfaceof the dielectric material.
 20. The structure of claim 14, wherein aportion of the dielectric material is interposed between the void andthe substrate.